1. Technical Field
The present invention relates to a printing apparatus and a method of controlling a printing apparatus.
2. Related Art
An ink jet printer allows an ink filled into an ejection unit to be ejected and forms an image on a recording medium by allowing a piezoelectric element provided in the ejection unit to be driven by a driving signal.
However, when the ink in the ejection unit is thickened, ejection abnormality occurs and the image quality of the image to be printed is degraded in some cases. Further, in a case where the ink in the ejection unit includes bubbles or paper dust is adhered to the vicinity of a nozzle of the ejection unit, ejection abnormality occurs and the image quality of the image to be printed is degraded in some cases. Accordingly, it is preferable to inspect an ejection state of the ink in the ejection unit for realizing high grade printing.
JP-A-2013-028183 discloses a technique of detecting residual vibration generated by allowing the piezoelectric element to be driven by the driving signal and inspecting the ejection state of the ink in the ejection unit based on detection results.
However, the inspection of the ejection state of the ink in the ejection unit is performed using residual vibration when the piezoelectric element is driven such that the ink is not ejected from the ejection unit. In a case where the inspection of the ejection state is performed without allowing the ink to be ejected, the inspection can be performed when the ejection unit is located in a position in which the ink can be ejected to the recording medium while the printing process is performed or the like. Therefore, it is possible to detect ejection abnormality in real time and to prevent the printing process from being delayed by the inspection.
However, in order to perform the inspection of the ejection state without allowing the ink to be ejected, it is necessary to set a waveform of a driving signal such that the piezoelectric element is driven to a degree that the ink is not ejected from the ejection unit. For this reason, there is a problem in that the ink is ejected in the inspection so that the recording medium is stained with the ink in a case where the waveform of the driving signal is not appropriately set.
Particularly, even in a case where the waveform of the driving signal is set such that the ink is not ejected, the ink is ejected when the piezoelectric element is driven by the driving signal if the viscosity of the ink or the temperature of the ejection unit is changed.